Yes uit is easy. Just do it.
However, Theresa's answer is not quite correct as far as Sky Viewing Cards and Freesat are concerned.
Without a Viewing Card, any Sky box will receive all the Free to Air (unencrypted) channels.
Any old Sky Viewing Card will allow you to view all the Free to View channels. (That is to say, those that are encrypted but do not require a Sky subscription.) If it has not been used for some time, it can take up to three days in the box to 'come alive'. As you have a card you do not need to buy a 'Freesat from Sky' (NOT Freesat - see below) card from Sky.
Alternatively you could buy a Freesat (Freesat not BBCFreesat) receiver (about £50) or Freesat HD receiver (about £100) which will, plug right in and receive all of the Freesat Channels. www.freesat.co.uk/ The advantage of this approach is that the EPG is better than using the Sky EPG.
T, April 2009